Subject: Re: [PATCH v2 2/2] dma-contiguous: Use fallback alloc_pages for single pages

From: Nicolin Chen <[email-masked]>
Date: Fri, 23 Aug 2019 15:11:04 -0700

On Fri, Aug 23, 2019 at 09:49:46PM +0900, Masahiro Yamada wrote:
> On Tue, May 7, 2019 at 7:36 AM Nicolin Chen <[email-masked]> wrote:
> >
> > The addresses within a single page are always contiguous, so it's
> > not so necessary to always allocate one single page from CMA area.
> > Since the CMA area has a limited predefined size of space, it may
> > run out of space in heavy use cases, where there might be quite a
> > lot CMA pages being allocated for single pages.
> >
> > However, there is also a concern that a device might care where a
> > page comes from -- it might expect the page from CMA area and act
> > differently if the page doesn't.
> >
> > This patch tries to use the fallback alloc_pages path, instead of
> > one-page size allocations from the global CMA area in case that a
> > device does not have its own CMA area. This'd save resources from
> > the CMA global area for more CMA allocations, and also reduce CMA
> > fragmentations resulted from trivial allocations.
> >
> > Signed-off-by: Nicolin Chen <[email-masked]>
> 
> 
> This commit (bd2e75633c8012fc8a7431c82fda66237133bf7e)
> broke the DMA for my MMC driver in the following way:
> 
> 
> 
> 
> [    1.876755] mmc0: ADMA error
> [    1.883385] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
> [    1.889834] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
> [    1.896284] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
> [    1.902733] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
> [    1.909182] mmc0: sdhci: Present:   0x01ff02f6 | Host ctl: 0x00000019
> [    1.915631] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
> [    1.922081] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000fa07
> [    1.928530] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
> [    1.934981] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
> [    1.941429] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
> [    1.947880] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
> [    1.954329] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
> [    1.960778] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
> [    1.967229] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
> [    1.973678] mmc0: sdhci: Host ctl2: 0x00000000
> [    1.978125] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
> [    1.985271] mmc0: sdhci: ============================================
> [    1.991758] mmc0: error -5 whilst initialising MMC card
> [    1.991913] 43fb0000.uart: ttyS1 at MMIO 0x43fb0000 (irq = 0,
> base_baud = 768000) is a 16550A
> [    2.011011] hctosys: unable to open rtc device (rtc0)
> [    2.017694] Freeing unused kernel memory: 2368K
> [    2.027131] Run /init as init process
> Starting syslogd: OK
> Starting klogd: OK
> Initializing random number generator... [    2.074399] random: dd:
> uninitialized urandom read (512 bytes read)
> done.
> Starting network: OK
> [    2.109593] mmc0: ADMA error
> [    2.112488] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
> [    2.118941] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
> [    2.125389] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
> [    2.131840] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
> [    2.138289] mmc0: sdhci: Present:   0x01ff02f6 | Host ctl: 0x00000019
> [    2.144738] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
> [    2.151188] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x00004e47
> [    2.157637] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
> [    2.164087] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
> [    2.170536] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
> [    2.176987] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
> [    2.183435] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
> [    2.189886] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
> [    2.196335] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
> [    2.202784] mmc0: sdhci: Host ctl2: 0x00000000
> [    2.207232] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
> [    2.214379] mmc0: sdhci: ============================================
> 
> [    2.220881] mmc0: error -5 whilst initialising MMC card
> Welcome to Buildroot
> buildroot login: [    2.332786] mmc0: ADMA error
> [    2.335668] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
> [    2.342119] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
> [    2.348568] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
> [    2.355018] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
> [    2.361468] mmc0: sdhci: Present:   0x01ff02f6 | Host ctl: 0x00000019
> [    2.367917] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
> [    2.374367] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000f447
> [    2.380816] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
> [    2.387267] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
> [    2.393716] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
> [    2.400166] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
> [    2.406615] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
> [    2.413065] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
> [    2.419515] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
> [    2.425963] mmc0: sdhci: Host ctl2: 0x00000000
> [    2.430412] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
> [    2.437557] mmc0: sdhci: ============================================
> [    2.444031] mmc0: error -5 whilst initialising MMC card
> [    2.572203] mmc0: ADMA error
> [    2.575089] mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
> [    2.581540] mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x00000002
> [    2.587989] mmc0: sdhci: Blk size:  0x00007200 | Blk cnt:  0x00000001
> [    2.594439] mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000013
> [    2.600889] mmc0: sdhci: Present:   0x01ef02f6 | Host ctl: 0x00000019
> [    2.607339] mmc0: sdhci: Power:     0x0000000b | Blk gap:  0x00000000
> [    2.613788] mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000e8c7
> [    2.620237] mmc0: sdhci: Timeout:   0x0000000b | Int stat: 0x00000001
> [    2.626686] mmc0: sdhci: Int enab:  0x03ff008b | Sig enab: 0x03ff008b
> [    2.633137] mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
> [    2.639586] mmc0: sdhci: Caps:      0x546ec800 | Caps_1:   0x00000000
> [    2.646036] mmc0: sdhci: Cmd:       0x0000083a | Max curr: 0x00000000
> [    2.652485] mmc0: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0xffffffff
> [    2.658936] mmc0: sdhci: Resp[2]:   0x320f5903 | Resp[3]:  0x3fd05e00
> [    2.665384] mmc0: sdhci: Host ctl2: 0x00000000
> [    2.669832] mmc0: sdhci: ADMA Err:  0x00000001 | ADMA Ptr: 0x000000013965b200
> [    2.676979] mmc0: sdhci: ============================================
> [    2.683450] mmc0: error -5 whilst initialising MMC card
> 
> CTRL-A Z for help | 115200 8N1 | NOR | Minicom 2.7.1 | VT102 | Offline
> | ttyUSB0
> 
> Reverting this commit fixed the problem.

We are having another problem with the new API and Christoph
submitted a patch at: https://lkml.org/lkml/2019/8/20/86

Would it be possible for you to test to see if it can fix?

We can revert my fallback change after all, if Christoph's
patch doesn't work for you either.

Thanks
Nicolin

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